Everything you always wanted to know about swingers.

I've never seen this discussed in the Forums and thought I'd ask about bedroom doors standing open or just ajar at house parties, hotel parties, or conventions with people playing in the rooms. Is that an open invitation to enter and join in? Is it an 'oops'? Is it an invitation to look but not touch?

How have you responded when you've walked past an open door with people playing in full view? Ignore it? Join them? Stand and watch?